Optimum design of composite laminated plates via a multi-objective function

This paper deals with the optimum design of composite laminated plates under stiffness and gauge constraints. A multi-objective function which combines the plate weight and the strain energy stored in the plate by weighting parameters is introduced. This objective function is minimized while satisfying constraints such as the structural deformation and the limits on design variables. Both ply orientation angles and ply thicknesses of the composite plate are used as the design variables. The stiffness analysis is performed by the finite element method in which a triangular element is used that is suitable for the analysis of thin to thick plates and includes the transverse shear effects. Analyses of the derivatives of the objective function and the constraint functions with respect to the design variables is performed analytically. The mathematical programming method called the constrained variable metric is used to solve this optimum problem. An example is provided for the optimal design of a rectangular laminated plate.     

A simple mixed-based approach for thin-walled composite blades with two-cell sections

In this work, a mixed beam approach that combines both the stiffness and the flexibility methods has been performed to analyze the coupled composite blades with closed, two-cell cross-sections. The Reissner’s semi-complementary energy functional is used to derive the beam force-displacement relations. Only the membrane part of the shell wall is taken into account to make the analysis simple and also to deliver a clear picture of the mixed method. All the crosssection stiffness coefficients as well as the distribution of shear across the section are evaluated in a closed-form through the beam formulation. The theory is validated against experimental test data, detailed finite element analysis results, and other analytical results for coupled composite blades with a two-cell airfoil section. Despite the simple kinematic model adopted in the theory, an accuracy comparable to that of two-dimensional finite element analysis has been obtained for cases considered in this study.     

基于最终失效强度的层合板结构的鲁棒优化分析

采用有限元方法分析复合材料层合板结构的最终失效强度，并以此对结构进行优化和鲁棒优化分析。层合板结构同时承受面内和面外载荷，每个单层板考虑基体失效和纤维断裂两种失效模式。当某一单层失效后采用比率退化法计算结构新的刚度，然后重新进行结构分析，直到求得结构的最终失效强度。以纤维方向角和层合板厚度作为设计变量，最终失效强度为目标，对结构进行优化。在此基础上，考虑了层合板结构的鲁棒优化分析。     

Stiffness Analysis of Corrugated Flexure Beam Used in Compliant Mechanisms

Conventional flexible joints generally have limited range of motion and high stress concentration. To overcome these shortcomings, corrugated flexure beam(CF beam) is designed because of its large flex...     

轻质复合材料天线辐射梁单元研究

为解决传统钢制大型天线辐射梁单元重量大、重复安装精度差、易腐蚀等问题,采用钢制球形接头与碳纤维复合材料管材胶接组合的方式,对复合材料管材和胶接接头进行了合理设计,成功制造出某大型天线轻质复合材料辐射梁单元。对此辐射梁单元进行了有限元分析与实测研究,能够很好地满足天线使用要求。结果表明：与传统的钢制辐射梁单元相比,复合材料天线辐射梁单元减重50％左右,辐射梁刚度好、强度大,安装一致性好、精度高,特别适合重复安装的大型天线。     

Vibration analysis of composite pipes using the finite element method with B-spline wavelets

A finite element formulation using the B-spline wavelets on the interval is developed for modeling the free vibrations of composite pipes. The composite FRP pipe element is treated as a beam element. The finite pipe element is constructed in the wavelet space and then transformed to the physical space. Detailed expressions of the mass and stiffness matrices are derived for the composite pipe using the B-spline scaling and wavelet functions. Both Euler-Bernoulli and Timoshenko beam theories are considered. The generalized eigenvalue problem is formulated and solved to obtain the modal characteristics of the composite pipe. The developed wavelet-based finite element discretization scheme utilizes significantly less elements compared to the conventional finite element method for modeling composite pipes. Numerical solutions are obtained to demonstrate the accuracy of the developed element, which is verified by comparisons with some available results in the literature.     

165MN自由锻造油压机组合梁强度分析研究

如何使组合梁的强度刚度达到设计要求是大型锻压机设计的关键技术之一.利用非线性结构分析软件Marc的接触模块,对165MN大型自由锻造油压机组合结构的下横梁进行了三维接触有限元分析,研究了在满载工况下的应力及变形.结果表明:锻压机在三缸工作时,下横梁的变形较小,下横梁受到的各个方向应力均小于许用应力,研究方法和结果将为大型锻压机组合梁的设计提供指导.     

桁架门式起重机主梁结构的优化设计

以起重机主梁总质量最小为目标函数,以主梁桁架构件的截面尺寸和桁架高度为设计变量,以强度、刚度为约束,应用有限元分析软件ANSYS对桁架门式起重机主梁桁架结构进行了优化设计,得到起重机结构主梁构件的主要参数.     

复合材料起落架舱门结构优化设计

基于有限元软件ANSYS建立复合材料起落架舱门参数化有限元模型,基于三明治夹芯板理论将蜂窝芯层等效为均质的厚度不变的层板,以蜂窝夹芯高度与复合材料面板各铺层厚度为设计变量,以铺层板、蜂窝夹芯的强度,结构稳定性以及结构刚度为约束函数,以结构质量最轻为目标函数,基于ANSYS优化模块首先选择零阶法进行优化得到粗略解,其次选择一阶梯度优化法进一步对夹层结构进行优化设计,得到最优蜂窝芯子厚度、蒙皮各铺层厚度.     

A simplified analysis method for composite beams with interlayer slip

A simplified static procedure is proposed for analysing and designing composite beams with interlayer slip. The method is parallel to the Eurocode 5 method, but it is general in nature and can be applied to arbitrary boundary and loading conditions. In contrast with Eurocode 5, a general and correct way of choosing the effective beam length of the problem is given by the present procedure, which is that the effective beam length equals the buckling length that is found in the corresponding column buckling problem. The procedure predicts the deflections and internal actions and stresses, in principle by replacing the fully composite bending stiffness (EI_∞) with the effective (partially) composite bending stiffness (EI_eff) in the expressions for these quantities in the corresponding fully composite beam. This effective bending stiffness depends on two non-dimensional parameters: the composite action parameter (shear connection stiffness) and the relative bending stiffness parameter. The method is applied to a number of simple practical cases and the results obtained have been compared with the exact values. The applicability of the simplified analysis procedure was found to be very good, except for interlayer shear stresses. The error in the Eurocode 5 procedure, as compared with the method proposed in this paper, can in some cases be up to almost 30% depending on the boundary conditions.     

基于神经网络和遗传算法的液压机上梁轻量化和刚度优化设计

提高刚度和轻量化是液压机设计中重点研究的内容。针对传统设计方法难以解决上梁刚度和轻量化之间的矛盾问题,提出了基于神经网络和遗传算法的液压机上梁轻量化和刚度优化设计方法。在液压机设计过程中,建立了上梁有限元分析的参数化模型。采用正交试验设计安排试验方案,获取试验数据。以试验数据为训练和检测样本,建立了设计参数与刚度和质量目标之间的非线性映射关系的神经网络模型。运用NSGA-Ⅱ遗传进化算法对神经网络模型进行优化,在指定参数区域内找出设计参数的Pareto最优解集。结果表明:该方法对于液压机上梁的多目标优化具有明显的效果。     

卫星相机快门装置的模态分析及刚度优化

为了研究卫星相机快门装置动态结构刚度,利用ANSYS Workbench对快门装置进行了有限元模态分析,得出该装置的固有频率和模态.在有限元建模中采用以弹簧单元代替滚珠的滚动轴承部件的简化建模方法,通过对简化样机进行模态试验,验证了简化建模方法的准确性.根据模态分析结果,以快慢盘的6个尺寸参数为设计变量,以其基频为目标函数,进行了快门装置的刚度优化设计,提高了装置的基频,使装置结构达到了设计性能指标.     

考虑连接性的三明治阻尼复合结构拓扑优化设计

三明治阻尼复合结构的力学性能取决于阻尼层材料的性能,综合考虑该结构的阻尼性能和可制造性要求,提出了一种面向结构宏观性能并考虑连接性的三明治阻尼复合结构拓扑优化设计方法。以最大化结构模态阻尼比为目标,考虑微结构刚度相材料的连接性,通过组合强制性连接约束法和非线性扩散法,构建了连接性约束下的阻尼复合材料微结构的优化设计模型,并结合3D打印技术实现了三明治阻尼复合结构的制造。运用所提方法对典型结构进行优化设计,得到了刚度相保持连接的阻尼复合结构,且优化后的结构阻尼变大,结构的频率响应变小,实现了三明治阻尼复合结构材料结构设计制造协同优化设计。仿真和实验结果表明,在微结构上存在最优的阻尼材料体积分数使优化后的三明治结构频率响应最小。     

扭转刚度测试方法及对构架疲劳强度影响

根据构架在线路运行中的扭曲状态和标准JIS E 4207：2004《铁路车辆-转向架-转向架构架设计通则》中规定的构架扭转刚度测试方法提出改进的刚度测试方法,新的测试方法简单且实用性较强,误差有效地控制在7%之内。构架根据结构设计形式的不同分为管梁型构架及箱梁型构架。利用新的扭转刚度测试方法分别对管梁型构架及箱梁型构架进行扭转刚度测试,同时理论分析两种类型构架扭转刚度不同的原因。利用ANSYS仿真分析软件对两种类型的转向架构架进行仿真分析,得出：构架扭转刚度的大小主要取决于测量的横截面积及横梁的结构形式,管梁型结构构架扭转刚度小于箱梁型结构构架的扭转刚度;在构架受扭转变形影响较大的区域,如横梁与侧梁的连接位置,由于箱梁型构架扭转模态频率较高,其动应力幅值较管梁型构架要小。     

车身动态刚度链建模及正向概念设计研究

提出了车身正向概念设计流程,由车身A级面及整车总布置方案建立了车身简化几何模型,确定了22个车身主断面位置,并以主断面属性为设计变量,基于梁单元理论与传递矩阵法得到模态坐标系下的车身动态刚度链数学模型,建立了主断面属性与车身固有频率的关系。以车身轻量化为目标函数,以车身静刚度与固有频率为约束条件对车身进行优化,采用遗传算法求解,确定优化后的各主断面属性参数。通过对比近似标杆车的静刚度与模态分析结果验证了动态刚度链设计方法的可行性。     

基于双向渐进结构优化法的柔性机构设计

基于双向渐进结构优化法提出一种面向柔性机构的拓扑优化设计策略。由于采用0/1离散拓扑设计变量和启发式变量更新机制,双向渐进结构优化法一般适用于结构刚度相关的凸优化设计问题。柔性机构以最大化驱动端的位移为设计目标,属于典型的非凸优化问题,难以直接应用该方法开展相应的设计。针对于此,通过定义一种由驱动位移和刚度特性（柔顺度）加权平均的优化目标函数,实现基于双向渐进结构优化法的柔性机构设计。该优化目标函数具有双重功效：（1）通过逐步（设计迭代步）衰减刚度特性的贡献,实现优化问题由刚度设计向驱动设计的动态演化,可应用双向渐进结构优化法开展机构的拓扑构型设计;（2）通过调节加权系数,实现对设计机构的驱动性能和刚度特性的灵活匹配调控,可有效抑制铰链的形成、防止应力集中引起的失效。典型算例的设计结果显示,提出的发展的演化式设计策略可实现稳健且高效的柔性机构设计。     

Effect of train carbody’s parameters on vertical bending stiffness performance

Finite element analysis(FEA) and modal test are main methods to give the first-order vertical bending vibration frequency of train carbody at present, but they are inefficiency and waste plenty of time. Based on Timoshenko beam theory, the bending deformation, moment of inertia and shear deformation are considered. Carbody is divided into some parts with the same length, and it’s stiffness is calculated with series principle, it’s cross section area, moment of inertia and shear shape coefficient is equivalent by segment length, and the fimal corrected first-order vertical bending vibration frequency analytical formula is deduced. There are 6 simple carbodies and 1 real carbody as examples to test the formula, all analysis frequencies are very close to their FEA frequencies, and especially for the real carbody, the error between analysis and experiment frequency is 0.75%. Based on the analytic formula, sensitivity analysis of the real carbody’s design parameters is done, and some main parameters are found. The series principle of carbody stiffness is introduced into Timoshenko beam theory to deduce a formula, which can estimate the first-order vertical bending vibration frequency of carbody quickly without traditional FEA method and provide a reference to design engineers.     

Exact dynamic analysis of composite beams with partial interaction

The partial differential equations and general solutions for the deflection and internal actions and the pertaining consistent boundary conditions are presented for composite Euler-Bernoulli members with interlayer slip subjected to general dynamic loading. Both free and forced vibrations are treated. The solutions are shown to be unique and complete under certain conditions, and valid for all so-called restricted admissible boundary conditions. Specifically, the exact eigenmode length coefficients are derived for the four Euler BC. They differ from those valid for ordinary, fully composite (solid) beams, except for the pinned-pinned case. The maximum deviation for beams with the other three Euler BC is shown to be less than 2-6% with respect to the eigenmode length coefficient and 3-10% with respect to the eigenfrequency, respectively, depending on the two non-dimensional parameters, composite action or shear connector stiffness and relative bending stiffness parameters. However, these deviations occur in a rather narrow range of the determining parameters, so for most practical cases the eigenmode length coefficients given for solid (fully composite) beams can approximately be used also for partially composite beams. The procedures of analysing beam vibrations are applied to a specific case. These solutions illustrate the effect of interlayer connection on the peak velocity of the beam vibrations. The proposed analytical theory is verified by tests and finite element calculations.     

Estimation of contact stiffness at interfaces in machine structures by a beam model on an elastic foundation

The dynamic properties of machine structures are significantly influenced by an interaction at the mating surfaces of machine elements. This interaction is called contact stiffness, and the development of a simple method for contact stiffness estimation is an important tribological objective. In this paper the contact stiffness is estimated by a beam model vibrating on an elastic foundation. The effects of clamping condition and mating surface topography on the contact stiffness obtained are quantitatively and accurately represented by experimental equations.     

纤维复合材料的可靠性优化研究

采用遗传算法分析有初始缺陷的层合板的可靠性优化问题.初始缺陷、强度参数为随机变量,采用一阶矩法分析单元层的可靠性,每个单层板考虑基体破坏和纤维断裂两种失效模式,系统失效概率的计算基于最终层失效理论.以纤维方向角和层合板厚度为设计变量,系统可靠度最小为目标,采用遗传算法计算优化问题.数值算例说明方法的有效性,分析不同失效理论时的最优解.